Stairs, Ramps, and Slopes
Design opportunities can emerge from the need to comply with code constraints, to specify proper rise and run dimensions, or to develop nosing details for stairs.
With few exceptions, ramps are limited in their slope to a maximum pitch of 1:12. Added design constraints include their minimum width and maximum length before required landings.
Handrails and guardrails have constraints of height, minimum openings between vertical members, and spatial clearances.
In addition, materials and detailing of various components, including seams, joints, and openings, need to take into consideration aspects of health, safety, and welfare issues as well as applied forces.
Prior to focusing on stairs, ramps, and slopes in detail, it would be helpful to expand upon the requirements that influence selection of their material aspects.
Design intentions are largely drawn by the need and desire to direct movement through space. Stairs, ramps, and slopes can serve as "sociopetal" elements that direct the perception of the space inward to define a central gathering area.
Conveyance systems can also serve as "sociofugal" elements, guiding human perception outward, away from a central space, extending views beyond a contained frame of reference.
Stairs, ramps, and slopes can be conceived as figural, clearly identifiable components, such as the central monumental stair under the Louvre's glass pyramid atrium space, designed by Pei Cobb Freed & Partners.
Stairs can also be conceived as anonymous spatial components, almost completely incorporated into the building's form, as in the Casa da Música in Porto, Portugal, designed by Rem Koolhaas of OMA.
The combination of handrails, joinery, and detail required by the assembly and material limitations of stairs, as well as the materiality of the walking surfaces, establishes primary design opportunities that ought to be considered holistically.
Le Corbusier's passion for both light and form developed out of a purist aesthetic and the emerging modern perspective of the machine age. Le Corbusier used simple geometric forms and plain surfaces as an effective means to articulate space and form. Such was the case with the spiral stair in the Villa Savoye. The stair was carefully dressed in white plaster to create a fluid and continuous vertical element that visually and viscerally moves one through space.
Stairs: Accessibility and Egress
Stairs are classified into two types: monumental stairs and means of egress.
Monumental stairs are not considered legal means of egress in a building. They are, however, prominent interior features that shape and influence the arrangement and organization of open space.
Basic stair configurations include scissor, straight-run linear, simple return, curved, cylindrical, spiral, L-shaped, and angled.
The minimum width of stairs, the rise and run of the stair treads, and the heights of handrails and guardrails are all influenced by the building codes, but primary design considerations lie in the spatial experience and spatial organization of both the building and its interconnected interior spaces.
Means of Egress
A means of egress is an enclosed exit stairway whose central purpose is to help people safely egress a building during a fire. Building codes establish dimensional constraints and influence the detail of fire-rated enclosures.
Treads and Risers
Stairs should have uniform treads and risers that do not deviate more than 0.25 inches (0.64 centimeters). As a general rule, stairs should have closed risers of uniform height, and treads should be slip-resistant.
Ramps and Slopes: Accessibility and Egress
Ramps that rise more than six inches (15 centimeters) or are longer than 72 inches (183 centimeters) require handrails and/or guardrails on both sides.
Handrails need to extend at least 12 inches (30 centimeters) beyond the top and bottom of the ramp. There must also be a clear space of 1.5 inches (3.8 centimeters) between the handrail and an adjacent wall, and the handrail must be between 34 and 36 inches (86 and 91 centimeters) above the ramp surface.
Handrails must be continuous. Horizontal openings greater than four inches (ten centimeters) in guardrails are prohibited by code.
Inclined flooring surfaces that are considered slopes do not require the use of either guardrails or handrails. A ramp is distinct from a slope by definition. A ramp is a surface that has a running slope greater than 1:20, while a slope is a surface with a running slope less than 1:20.
Ramps must not exceed a maximum slope of 1:12 unless specified by extenuating situations. Ramps may not exceed 30 feet (nine meters) in length or extend higher than a maximum allowable rise of 30 inches (76 centimeters) before requiring a landing.
Landings must be level, as wide as the ramp itself, and 60 inches (152 centimeters) long. If a ramp changes direction, the landing should be a minimum of 60 by 60 inches. Surfaces of ramps and slopes must be slip-resistant.
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Nancy Gesimondo is an adjunct professor at the Fashion Institute of Technology in New York City. She has taught design studio and materials courses in various interior design programs for ten years. She is currently the principal of a high-end residential design practice in New York City.
Jim Postell is an associate professor in the College of Design, Architecture, Art, and Planning at the University of Cincinnati. He has taught design studio and seminar courses for 25 years and maintains an active design practice. He is the author of Furniture Design.
This article is excerpted from Materiality and Interior Construction by Nancy Gesimondo and Jim Postell, copyright © 2011, with permission of the publisher, John Wiley & Sons.